56 Southern Cross. 



are the "daughter" teeth almost e([ual in size ti» the remaining 

 individuals of the series. 



(III.) In four of these five cases, on the above reasoning, the 



extra tooth is apparently the product of m. — . In one only 



(No. 324&) is it apparently the product of p.m. — . 



(IV.) In addition to the above, there occur several instances of 

 what, following the above suppositions, can only be regarded as 

 abortive or incomplete division or reduplication of teeth. Such 

 abortive reduplication may be of two kinds. 



(V.) Either it occurs (a) as if by some kind of sympathy in a 

 tooth closely related to an individual supposed to have undergone 

 reduplication, either on the opposite side of the same jaw or in the 

 opposite jaw. Thus in No. 3246 (a highly interesting specimen, since 



it presents the only instance of reduplication in p.m. — , — the only 



instance of complete reduplication on one side accompanied by only 

 abortive reduplication on the other — also the only instance of, in addi- 

 tion to the above, abortive variation in m. — — in which the formula 



6x5 

 is p.m. and m. A, all the first premolars being halfway along 



X D 



the road to division. Each, although singly rooted, is provided with 

 two, in most cases quite distinct and perfect, crowns, and is grooved 

 along the most probable line of division into two teeth. 



(VI.) or (&) it may occur independently, as has happened in the 



case of m. —of the same head (No. 3246), or in p.m. — , of No. 2. 



4 



(VII,) In addition to the supposed reduplication or splitting a 

 very wide range of variation is observable in regard to the rooting 

 of the teeth. Almost any of these, except the fii'St premolars, 

 may appear either with two perfect roots or with a single root 

 only. 



(VIII.) But between these forms there are many gradations 

 represented by flattened single roots — flattened single roots grooved 

 along the plane where a division into two roots would occur— flattened 

 single roots in which incipient division is indicated by a terminal 

 notch and all stages of development of this terminal notch, until it 

 becomes a cleft deeply di\iding the pillars of a fully developed 

 double root. These gradations are most easily seen in the teeth of a 

 single head, such as the lower molars of No. 3246 or of No. 700 : 



